1. Field
The present invention relates to a rechargeable battery and a rechargeable battery module including the rechargeable battery.
2. Description of the Related Art
A rechargeable battery can be repeatedly charged and discharged, unlike a primary battery. A rechargeable battery of a small capacity is used for a small portable electronic device like a mobile phone or a laptop computer and a camcorder, and a rechargeable battery of a large capacity is used as a power source for driving a motor of a hybrid vehicle and an electric vehicle.
A rechargeable battery may be used as a single battery cell, as in a small electronic device, or may be used in a module state in which a plurality of battery cells are electrically connected, as in use for driving a motor. A rechargeable battery module is formed by connecting electrode terminals of unit battery cells with a busbar.
The rechargeable battery has a negative electrode terminal that is connected to a negative electrode of the electrode assembly and a positive electrode terminal that is connected to a positive electrode thereof. For example, the negative electrode and the negative terminal may be made of copper, and the positive electrode and the positive terminal may be made of aluminum.
One side of each of the negative and positive lead tabs is connected to a negative electrode and a positive electrode, respectively, and the other side thereof is connected to negative and positive electrode terminals, respectively. For this purpose, negative and positive electrode lead tabs are made of copper and aluminum, respectively.
Therefore, when forming a rechargeable battery module, typically a busbar that connects negative and positive electrode terminals of a unit battery cell is formed with a copper portion and an aluminum portion corresponding to the negative electrode terminal and the positive electrode terminal, respectively. In other words, the busbar integrally has a copper portion and an aluminum portion, wherein the copper portion is laser welded to the negative terminal, and the aluminum portion is laser welded to the positive terminal.
In this case, it may be difficult to weld a negative terminal that is made of copper and a copper portion of a busbar with present commercial technology. In other words, a welding quality of connections of negative and positive terminals of an adjacent unit battery cell with a busbar may be deteriorated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.